With the dramatic growth of fiber optic communications systems, devices for processing optical signals have become increasingly important. Planar devices comprising optical waveguides fabricated on planar substrates offer a promising environment for receiving and processing signals from optical fibers. These waveguides are used in OIC devices for optical signal processing. A variety of methods have been suggested for the manufacture of high-silica content glass articles, such as the single and double dispersion processes described by D. W. Johnson, et al. in Fabrication Of Sintered High-Silica Glasses, U.S. Pat. No. 4,419,115, and the process described by D. W. Johnson, et al in Sintered High-Silica Glass And Articles Comprising Same, U.S. Pat. No. 4,605,428. Sol gel techniques for making optical quality glass bodies are described by Chandross et al. in U.S. Pat. No. 5,240,488. That patent provides the basic sol gel process for these applications and is incorporated herein in its entirety for providing that process information.
A variety of approaches may be considered for making planar waveguide structures. For example, chemical vapor deposition (CVD) is widely used in silicon technology for producing thin films of SiO2. However, CVD SiO2 grows only fractions of a micrometer per hour. Thin silica films on silicon wafers may also be produced by growing oxide directly on a silicon wafer by standard high pressure oxidation. This approach is attractive since the processing and patterning of SiO2 layers on silicon is well developed. However, again, this growth is slow and the practical film thickness is limited to about 15 micrometers and can be used only as an undercladding for waveguiding devices.
Other glasses, such as sodium-boro-silicate glass, can be formed in thin films, but it is difficult to make such films that are suitable for optical waveguide applications.
A simple, rapid, and economical technique for making optical quality glass planar waveguide structures would constitute an important contribution to the technology.